International Cooperative Study of ELF VLF Electromagnetic Noises

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As one of the eight stations on the globe, the Stanford University ELF VLF Radiometer were set at the Earth Observatory, Faculty of Science, Kochi University. Using data obtained so far we have made the following studies. 1. For analysing VLF electromagnetic noise waveforms. we have assumed the lightning current waveform as source a and made numerical calculations using the Fast Fourie Laplace Transform method. We have thus reasonably interpreted the observed waveforms.2. We have also analysed Whistler waveforms observed and interpreted the frequency dispersion and the amplitude characteristics. 3. And we have studied lightning characteristics which occurred at the magnetic conjugate areas in the northern part of Australia using the observed whistler data.4. We have made an automatic waveform recorder of ELF electromagnetic pulses and obtained many interesting waveforms including a very high Q value oscillations at 8 Hz which is the fundamental frequency in the earth-ionosphere cavity. 5. We have designed a waveform recorder of radio emission which will be emitted from cosmic ray showers, and made a test measurement. 6. The measuring system of the earth potential using ball antennas which are set under the ground surface. and made a detailed surveys of EM noises in the urban area. 7. We have carefully checked the ELF VLF Radiometer data and correlate them with the occurrence of earthquakes and found the EM noises which coincide (1) with the elastic wave arrival at the Observatory, and (2) with the emission time at the hypocenter. 8. We have obtained the electric field waveforms emitted from the rocks hit with a hammer in the EM shielded room. 9. A comprehensive survey has been made to locate the epicenters of the earthquakes which occurred recently in Shikoku.